1. Field of the Invention
The present invention relates to a display panel, and more particularly to a pixel structure of a display panel.
2. Description of Related Art
A thin film transistor liquid crystal display (TFT-LCD) mainly includes a thin film transistor (TFT) array, a color filter and a liquid crystal layer. FIG. 1 is a schematic view of a conventional TFT array substrate. Referring to FIG. 1, a TFT array substrate 100 mainly includes a plurality of pixel structures 110 arranged in array. Each of the pixel structures 110 includes a scan line 112, a data line 114, a TFT 116 and a pixel electrode 118, etc.
In brief, the TFT 116 is used as a switch element of each pixel structure 110 while the scan line 112 and the data line 114 are used to provide the selected pixel structure 110 with proper operating voltages for respectively driving the selected pixel structure 110 to display an image.
FIG. 2 is a schematic equivalent circuit drawing of a single pixel in a conventional TFT-LCD. Referring to FIG. 2, a single pixel of a conventional TFT-LCD generally comprises a thin film transistor 116, a liquid crystal capacitance CLC and a storage capacitance Cst.
Referring to FIGS. 1 and 2, the liquid crystal capacitance CLC is formed by coupling the pixel electrode 118 on the TFT array substrate 100 and a common electrode on the color filter (not shown). The storage capacitance Cst disposed on the TFT array substrate 100 is connected to the liquid crystal capacitance CLC in parallel. In addition, the gate G, the source S and the drain D of the TFT 116 are connected to the scan line 112, the data line 114 and the pixel electrode 118 forming the liquid crystal capacitance CLC, respectively. Since the gate G and the drain D of the TFT 116 are partially overlapped in an overlapping region, a gate-drain parasitic capacitance Cgd is existed between the gate G and the drain D.
Referring to FIG. 1 and FIG. 2 again, since there exists a specific relationship between a voltage applied the liquid crystal capacitance CLC(i.e. a voltage applied to the pixel electrode 118 and the common electrode) and a light transmittance of liquid crystal molecules, a predetermined image can be displayed by controlling the voltage applied the liquid crystal capacitance CLC in accordance with the desired predetermined image. Wherein, as the TFT 116 is off, the voltage applied on the liquid crystal capacitance CLC theoretically keeps unchanged, i.e. in a holding state. However, due to the presence of the gate-drain parasitic capacitance Cgd, the voltage kept by the liquid crystal capacitance CLC varies slightly with the changed signals on the data line 114, called a coupling effect. Therefore, the voltage kept by the liquid crystal capacitance CLC is eventually apart from the predetermined value.
Among current exposure processes for fabricating the TFT array substrate, adjoined photomasks of a stepper exposing machine are mostly used to perform the exposure process for forming the TFT array substrate. Therefore, a displacement error of movements of the stepper during the exposure process would cause nonconformity among the pattern positions in each shot. Particularly, among each of the shots, when the overlapping region of the gate G and the drain D of the TFT 116 as shown in FIG. 1 varies, the gate-drain parasitic capacitance Cgd in each of the shots is changed and thus the problem of uneven brightness, i.e. flicker, during displaying is occurred.